Copolymers of N-isopropylacrylamide can trigger pH sensitivity to stable liposomes.
Stable liposomes were rendered pH-sensitive by complexation to a polymer that undergoes marked temperature- and pH-dependent water solubility changes. The N-isopropylacrylamide-methacrylic acid copolymer was prepared with or without octadecyl acrylate. At pH below the phase transition of the polymer, egg phosphatidylcholine liposomes quickly released a part of their contents only when associated with the octadecyl aliphatic chain grafted polymer at 37 degrees C. Similarly, sterically stabilized liposomes also quickly released a significant part of the entrapped fluorescent markers at pH 5.5-4.9, values corresponding to those of endosomes/lysosomes. This new pH-sensitive liposome-polymer system may further improve the efficiency of liposomal drug delivery.
Meyer
O
O
Department of Cellular and Molecular Pharmacology, University of California, San Francisco 94143, USA.
Papahadjopoulos
D
D
Leroux
J C
JC
D000178:Acrylamides / Q000737:chemistry*; D004355:Drug Stability; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008081:Liposomes / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry*; D011109:Polymethacrylic Acids / Q000737:chemistry*
D000178:Acrylamides; D005456:Fluorescent Dyes; D008081:Liposomes; D010713:Phosphatidylcholines; D011109:Polymethacrylic Acids; C085085:poly(N-isopropylacrylamide-co-methacrylic acid)